'\" te
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.TH LIBC_DB 3LIB "Aug 19, 2019"
.SH NAME
libc_db \- threads debugging library
.SH SYNOPSIS
.nf
cc [ \fIflag\fR... ] \fIfile\fR... \fB-lc_db\fR [ \fIlibrary\fR... ]
#include <\fBproc_service.h\fR>
#include <\fBthread_db.h\fR>
.fi

.SH DESCRIPTION
The \fBlibc_db\fR library provides support for monitoring and manipulating
threads-related aspects of a multithreaded program. There are at least two
processes involved,  the controlling process and one or more target processes.
The controlling process is the \fBlibc_db\fR client, which links with
\fBlibc_db\fR and uses \fBlibc_db\fR to inspect or modify threads-related
aspects of one or more target processes. The target processes must be
multithreaded processes that use \fBlibc\fR. The controlling process might or
might not be multithreaded itself.
.sp
.LP
The most commonly anticipated use for \fBlibc_db\fR is that the controlling
process will be a debugger for a multithreaded program, hence the "db" in
\fBlibc_db\fR.
.sp
.LP
The \fBlibc_db\fR library is dependent on the internal implementation details
of \fBlibc\fR. It is a "friend" of \fBlibc\fR in the C++ sense, which is
precisely the "value added" by \fBlibc_db\fR. It encapsulates the knowledge of
\fBlibc\fR internals that a debugger needs to manipulate the threads-related
state of a target process.
.sp
.LP
To be able to inspect and manipulate target processes, \fBlibc_db\fR makes use
of certain process control primitives that must be  provided by the process
using \fBlibc_db\fR. The imported interfaces are defined in
\fBproc_service\fR(3PROC). In other words, the controlling process is linked
with \fBlibc_db\fR and calls routines in \fBlibc_db\fR. In turn, \fBlibc_db\fR
calls certain routines that it expects the controlling process to provide.
These process control  primitives allow \fBlibc_db\fR to:
.RS +4
.TP
.ie t \(bu
.el o
Look up symbols in a target process.
.RE
.RS +4
.TP
.ie t \(bu
.el o
Stop and continue individual lightweight processes ( LWPs) within a target
process.
.RE
.RS +4
.TP
.ie t \(bu
.el o
Stop and continue an entire target process.
.RE
.RS +4
.TP
.ie t \(bu
.el o
Read and write memory and registers in a target process.
.RE
.sp
.LP
Initially, a controlling process obtains a handle for a target process. Through
that handle it can then obtain handles for the component objects of the target
process, its threads, its synchronization objects, and its thread-specific-data
keys.
.sp
.LP
When \fBlibc_db\fR needs to return sets of handles to the controlling process,
for example, when returning handles for all the threads in a target process, it
uses an iterator function. An iterator function calls back a client-specified
function once for each handle to be returned, passing one handle back on each
call to the callback function.  The calling function also passes another
parameter to the iterator function,  which the iterator function passes on to
the callback function.  This makes it easy to build a linked list of thread
handles for a particular target process. The additional parameter is the head
of the linked list, and the callback function simply inserts the current handle
into the linked list.
.sp
.LP
Callback functions are expected to return an integer.  Iteration terminates
early if a callback function returns a non-zero value. Otherwise, iteration
terminates when there are no more handles to pass back.
.SH INTERFACES
The shared object \fBlibc_db.so.1\fR provides the public interfaces defined
below. See \fBIntro\fR(3) for additional information on shared object
interfaces.
.sp

.sp
.TS
l l
l l .
\fBtd_init\fR	\fBtd_log\fR
\fBtd_sync_get_info\fR	\fBtd_sync_get_stats\fR
\fBtd_sync_setstate\fR	\fBtd_sync_waiters\fR
\fBtd_ta_clear_event\fR	\fBtd_ta_delete\fR
\fBtd_ta_enable_stats\fR	\fBtd_ta_event_addr\fR
\fBtd_ta_event_getmsg\fR	\fBtd_ta_get_nthreads\fR
\fBtd_ta_get_ph\fR	\fBtd_ta_get_stats\fR
\fBtd_ta_map_addr2sync\fR	\fBtd_ta_map_id2thr\fR
\fBtd_ta_map_lwp2thr\fR	\fBtd_ta_new\fR
\fBtd_ta_reset_stats\fR	\fBtd_ta_set_event\fR
\fBtd_ta_setconcurrency\fR	\fBtd_ta_sync_iter\fR
\fBtd_ta_sync_tracking_enable\fR	\fBtd_ta_thr_iter\fR
\fBtd_ta_tsd_iter\fR	\fBtd_thr_clear_event\fR
\fBtd_thr_dbresume\fR	\fBtd_thr_dbsuspend\fR
\fBtd_thr_event_enable\fR	\fBtd_thr_event_getmsg\fR
\fBtd_thr_get_info\fR	\fBtd_thr_getfpregs\fR
\fBtd_thr_getgregs\fR	\fBtd_thr_getxregs\fR
\fBtd_thr_getxregsize\fR	\fBtd_thr_lockowner\fR
\fBtd_thr_set_event\fR	\fBtd_thr_setfpregs\fR
\fBtd_thr_setgregs\fR	\fBtd_thr_setprio\fR
\fBtd_thr_setsigpending\fR	\fBtd_thr_setxregs\fR
\fBtd_thr_sigsetmask\fR	\fBtd_thr_sleepinfo\fR
\fBtd_thr_tsd\fR	\fBtd_thr_validate\fR
.TE

.SH FILES
.ne 2
.na
\fB/lib/libc_db.so.1\fR
.ad
.RS 24n
shared object
.RE

.sp
.ne 2
.na
\fB/lib/64/libc_db.so.1\fR
.ad
.RS 24n
64-bit shared object
.RE

.SH ATTRIBUTES
See \fBattributes\fR(7) for description of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
MT-Level	Safe
.TE

.SH SEE ALSO
\fBIntro\fR(3), \fBtd_ta_new\fR(3C_DB), \fBattributes\fR(7),
.BR threads (7)
